1. Technical Field
The present invention relates to an optical filter, an analytical instrument, an optical apparatus, a method of manufacturing the optical filter, and so on.
2. Related Art
There has been proposed an interference filter having a variable transmission wavelength (JP-A-11-142752 (Document 1)). As shown in FIG. 1 of Document 1, there are provided a pair of substrate held in parallel to each other, and a pair of reflecting films formed on the pair of substrates so as to be opposed to each other and have a gap with a constant distance. The light beam entering a gap between the pair of reflecting films is multiply reflected on the same principle as a Fabry-Perot interferometer, and the light component in the wavelength band other than a specific wavelength band is canceled by interference while only the light component in the specific wavelength band is transmitted. By making the gap between the pair of reflecting films variable, the interference filter functions as a band-pass filter, and is called an etalon.
The pair of reflecting films can be formed of, for example, dielectric multilayer films shown in JP-A-2009-134028 (Document 2), or metal films assuring high reflectance. Further, a pair of substrates are respectively provided with bonding films, and each of the bonding films are bonded with the surfaces thereof activated (JP-A-2008-116669 (Document 3), Japanese Patent No. 4337935 (Document 4)).
In the bonding method of Document 3, the pair of substrates are bonded via the metal films (bonding films) provided respectively to the pair of substrates by solid state bonding. However, the solid state bonding of the metal film is affected by the surface roughness, and lacks bonding reliability.
Incidentally, in the bonding method according to Document 4, bonding is performed by activating the bonding film with ozone or ultraviolet radiation. It has turned up that in the activation process of the bonding film a pair of reflecting films formed of metal films or dielectric multilayer films might be damaged to be changed in quality or deteriorated, and thus the reflectance thereof might be degraded. The pair of reflecting films might be negatively affected by ozone or ultraviolet radiation depending also on the environment in which the optical filter is disposed.